Conversion of hydrocarbon oil



aromatic series.

Patented Dec. 8, 1942 CONVERSION OF HYDROCARBON OIL Charles W. Hussey,Chicago, IlL, assignor to Universal Oil Products Company, Chicago,lll.,'a corporation of Delaware Application August 31, 1939, Serial No.292,853

4 Claims. (01. 196-49) The invention relates more specifically to animproved process involving thermal cracking and catalytic cracking ofhydrocarbon oils in a cooperative and interdependent manner tosimultaneously produce regulated amounts of commercial motor gasolineand aviation-base gasoline in a unified system of relatively simple formwhich possesses construction and operating advantages and ahigh degreeof flexibility with respect to the relative proportions of the two typesof gasolines produced.

The catalytic cracking step of the process herein provided isspecifically directed to the type of reaction now known as "lowtemperature catalytic cracking which, when employ d to convert olefinicor olefin-containing hydroca on oil distillates, results in a productcontaining a high proportion of hydrocarbons oi the paramnic and I Asthe name implies, low temperature catalytic cracking also differs fromthe usual type of catalytic cracking operation, which is normallyconducted at temperatures of the order of 900 F. and higher, by thelower temperatures employed which may range, for example, from 500 to850 F under the usual op erating pressures and, wit

order of 650 to 800 F.

No novelty is claimed herein for either the low temperature catalyticcracking step or the thermal cracking step per se and the inventionresides Y in the novel and advantageous manner in 'which thermal and lowtemperature catalytic cracking are co-operatively combined. There isdefinite .co-operative relation between the two steps in that crackingstock for low temperature catalytic cracking is derived from the thermalcracking stage of the system at a temperature suitable for conductingthe desired catalytic cracking operation and, in the preferredembodiment of the invention, there is a further co-operative relationinthat, after'separating the desired relatively low end-pointaviation-base. gasoline from higher boiling conversion products of thelow tempera;- ture catalytic cracking step, the latter are preferablysupplied to the thermal cracking system at a point in the flow sequencetherein beyond that from which the charging stock for the catalyticcracking step is removed, (such as, for example, the fractionator of thethermal cracking system) whereby catalytically cracked gasoline ofhigher end-boiling point than said aviation-base gasoline is commingledwith" the gasoline produced by thermal crackingto form the final motor55 substantially reduced superatmospheric pressure,

gasoline product of the process and whereby thetype of catalyst which Ipreferably employ, are usually of the gher boiling fractions of the lowtemperature catalytically cracked products are included in the recyclestock subjected to thermal cracking.

One important advantage of the system herein 5 provided resides in itsadaptability to numerous existing thermal cracking systems, whereby thelatter may be readily remodeled to provide a system in which bothcommercial motor gasoline and aviation-base gasoline may be produced inregulated amounts by the simple additionof a minimum of low temperaturecatalytic cracking equipment, employing as charging stock a regulatedportion of the relatively clean vaporous conversion products formed inthe thermal crackingsyst'em and derived from the latter at a pointtherein at .which the temperature of the vapors is suitable forefiecting their desired conversion in the presence of the catalyst. Asapplied, for example, to the well known series chamber or my fullflashing type of thermal cracking system of either the single coil ormultiple coil variety, wherein hot .conversionproducts from one or morecracking coils are passed through a high pressure reaction chambermaintained at cracking '25 temperature, vaporous and liquid productsbeing removed in commingled state from the reaction chamber and suppliedto a reduced pressure vaporizing and separating chamber wherefromrelatively clean vaporous conversion products are supplied tofractionating equipment for the formation of refiux condensate andrecovery from the vapors of materials boiling within the range ofgasoline, the charging stock for the low tem- 4 perature catalyticcracking step of the present process is preferably a portion of saidrelatively clean vapors removed from the reduced pressure vaporizing andseparating chamber, the operating conditions .in the latter zone beingso controlled that the vapors may be supplied directly therefrom to thezone of catalytic reaction under temprature and pressure conditionsdesirable for conducting the low temperature catalytic crackingreaction. I

. The features of the invention are also readily applicable to manyother specific forms of thermal cracking systems including those such ascommon- 1y employedrfor the reforming treatment of gasoline, naphtha andthe like to improve its antiknock value, wherein conversion productsformed at high'temperature and 'superatmospheric pressure in thereforming coil are cooled to atemperature at which detrimental furthercracking will not occur and thence supplied directly to a vaporizing andseparating chamber operated at the charging stock for the lowtemperaturecatalytic cracking step likewise being derived, in such a system, fromthe reduced pressure vaporizing and separating chamber at the desiredtemperature and pressure level for conducting the low temperaturecatalytic operation.

The accompanying diagrammatic drawing illustrates one specific form ofapparatus in whicha combination thermal and catalytic cracking operationembodied by the invention may be conducted- The drawing is onlyillustrative, however, and it should be understood that the-invention isnot limited in its broader aspects to the specific operation describedin conjunction with the description of the drawing. I

Referring to the drawing, charging stock for the process, which maycomprise any desired type of hydrocarbon oil ranging from crudepetroleum or residual oil, such as topped or reduced crude, to lightdistillates, is supplied through line I and valve 2 to pump-3 by meansof which -it is fed through line 4 and may be directed, depending uponits characteristics, either through valve 5 in this line to the lightoil cracking coil 6 or through line 1, valve 8 and line 9 to the heavyoil cracking coil 10 or through line 1, line H and valve l2 tofractionator l3.

Either the light oil cracking coil or the heavy oil cracking coil, orboth, may be employed within the scope of the invention and when coil Iis utilized the oil supplied thereto is heated to the desired crackingtemperature during its passage therethrough, preferably at a substantialsuperatmospheric pressure. Heat for this cracking operation is derivedfrom furnace M in which 0011 i0 is disposed, The heated conversionproducts from coil in are directed through line l and'valve is intoreaction chamber I! which is optional equipment and is preferablyemployed when the oil to be cracked is of a relatively heavy nature orcontains a substantial quantity of highboiling components.

Chamber l1, when utilized, is preferably operated at a substantialsuperatrnospheric pres sure which may be substantially the same orsomewhat lower than that employed in the communicating heating coilutilizing the lowest outlet pressure and, although not illustrated inthe drawing, chamber I1 is preferably insulated tov conserve heat andmaintain an temperature inthis zone.

In the particular case here illustrated, both vaporous and liquidconversion products are directed from the lower portion ofg chamber I!through line I8, valve l9 and line 20 into vaporizmg and separatingchamber 2| which is preferably operatedat a substantially reducedsufperatmospheric pressure relative to that employed in chamber I1.

When cracking coil 6 is utilized, the relatively light hydrocarbon oilsupplied to this zone is heated, by means of heat supplied from furnace22, to the desired cracking temperature and the resulting heatedproducts discharged from this zone may be directed, all or in part,through line 23 and valve 24 into reaction chamber I! or all or in partthrough line 25, valve 26 and line 20 into vaporizing and separatingchamber 2|, the pressure in the latter zone preferably beingsubstantially lower than that employed at the outlet of coil 6.

Provision is made for introducing cooling oil through line 21 and valve28 into the stream of conversion products being supplied to chamberactive cracking 2|. for the purpose of retarding or arresting fur-- thercracking or these products and reducing the formation and deposition ofcoke or similar heavy carbonaceous materials. Any other suitresidualconversion products to coke in this zone or to produce a liquid residuewhich is removed from the lower portion of the chamber through linev 29and valve 30 to cooling and storage or to further treatment which may,when desired, involve, for example, further distillation to heavierresidual liquid, coke or pitch-like residue.

The invention contemplates the use of bubble trays, perforated pans orany other suitable well known form of fractionating or contact means,not' illustrated, within the upper portion of chamber 2| for thepurposeof substantially'freeing the vapors evolved in this zone of undesirableentrained or dissolved high coke-forming materials and to assist incleaning up the vapors in chamber 2| provision is made for introducing asuitable cooling oil into the upper portion of this zone through line 3|and valve 32. It is-also, of course, within the scope of the inventionto employ suitable partial condensing or rough fractionating equipmentsuch as a knock-out drum, heat exchanger or the like in line 33 throughwhich vapors are removed from chamber 2|, although this well knownexpedient is not illustrated in'the drawing. By control of the amount ofcooling accomplished within chamber 2 I or The materials supplied to'fractionator |3- which include vapors from chamber 2!, any

charging stock supplied to this zone and any conversion products of thelow temperature catalytic cracking step which maybe supplied to thiszone in the manner subsequently described, and therein fractionated toform an overhead vaporous stream consisting essentially of materialsboiling within the range of the desired final motor gasoline product ofthe process and gases, and to form reflux condensate consistingessentially 31 higher boiling fractions. The'fractionated vapors aredirected from the upper portion of fractionator I3 through line 31 andvalve 38 to condensation and cooling in condenser 39 wherefrom theresulting distillate and uncondensed gases are directed through line 40and valve 4| to collection and separation in receiver 42. Un-

- condensed gases areareleased from thereceiver through line 43 andvalve 44 to storage or elsewhere, as desired. The distillate whichcoinprises the motor gasoline product of the process treatment, notillustrated,'su ch as, for example,

stabilization, chemical treatment to improve its quality, or thelike.

When desired, regulated quantities of the distillate collected inreceiver 42 may be returned by well known means, not illustrated, to theupper portion of fractionator l3 to serve as a cooling and refluxingmedium in this zone.

The total reflux condensate formed in fractionator l3 may be directedfrom the lower porlected lighter fractions are removed from a suitableintermediate point in the fractionator through line' 52 and directedthrough valve 53 in this line to pump 54 wherefrom the relatively lightreflux condensate is supplied through line 55, valve 56 and line ,4 tothermal'cracking treatment ini-coil 6. It is also entirely within thescope of the invention to remove all or any portion of the condensatecondensed from the vaporous conversion products in fractionator l3 fromthe system by well known means, not illustrated.

The catalytic cracking step of the system .may employ one .or aplurality of catalytic reactors of any desired form and, in theparticular case here illustrated, two reactors 59 and Gil are provided.Each of the reactors contains a suitable catalyst which, in activestate,is capable of. promoting low temperature cracking of the vapors fromchamber 2|. Each of the reactors is alternately employed as a lowtemperature catalytic cracking zone and as a'zone for effectingreactivation of the catalyst in situ. This reactivation is necessitatedby the deposition of heavy carbonaceous materials on the catalyst duringthe low temperature catalytic cracking reaction and may be accomplishedin any wellknown manner which does -not constitute a novel part of thepresent invention and is, therefore, not illustrated.

-While reactor 59 is employed as the low temperature catalytic crackingzone, the vapors from line 35 are directed through line B] and valve 62into this zone wherein they contact the catalyst disposed therein andwherein the desired low temperature catalytic cracking reaction iseffected, the resulting conversion products being 64 and line 69 toseparating and fractionating column 10. i

While reactor 60 is employed as a low temconversion products aredirected through line '61, valve 68 and line 69 to vaporizing andfractionating column 10.

Preferably, since the low temperature catalytic cracking reaction isendothermic, any suitable well known means, not illustrated, is provided'for supplying heat to the reactor for maintaining the reactants and thecatalyst bed at a suitable reaction temperature and since regenerationof the catalyst is an exothermic reaction involving burning from thecatalyst particles of heavy carbonaceous materials deposited thereonduring the low temperature catalyticcracking reaction. provision isnormally made in any well known manner. not illustrated for preventingan excessive temperature rise in the catalyst bed during reactivationand thereby avoid damaging of the catalyst. v

In case the nature of the vapors subjected to low temperature catalyticcracking treatment,

the nature of the catalyst employed for pr'omoting the low temperaturecatalytic cracking reaction and the conditions of operation employed aresuch that any substantial quantity of heavy liquid conversion productsunsuitable for further cracking treatment in the thermal cracking stepof the system are formed, these materials are preferably separated fromthe lighter vaporous conversion products in the lower portion of colum10 and removed through line H and valve 12 to cooling and storage orelsewhere, as desired.

The vaporous conversion products, including materials boiling within therange of gasoline and heavier fractions suitable for further thermalcracking treatment, are fractionated in column I0 to separate therefromas fractionated vapors a stream consisting essentially of normallygaseous products and gasoline fractions of relatively low end-boilingpoint as compared with the motor gasoline recovered in receiver 42. Theend-boiling point of this stream may be varied to suit requirements, sothat the aviation-base gasoline recovered therefrom by condensation willcomprise substantially only the relatively light gasoline fractionswhich are essentially paraffinic and accordingly have a bromine numbermeeting market requirements for aviation gasoline. This stream isdirected from the upper portion of fractionator 10 through line 13 andvalve 14 to condensation and cooling in condenser l5, wherefrom theresulting distillate and uncondensed gases are directed through line I6and valve 11 to collection and separation in re- .directed fromreactor59 through line 63, valve iii ceiver 18. The uncondensed gasesare released from the receiver through line I9 and valve and theaviation-base gasoline is directed from this zone through line BI andvalve 82 to storage or elsewhere, as desired.

When desired, regulated quantities of the distillate collected inreceiver 18 may be returned by well known means, per portion off-ractionator 10 to serve as a cooling and refluxing medium in thiszone.

Those fractions of the catalytic conversion products supplied to column10, which boil above the range .of the desired aviation-base gasolineand include higher boiling fractions suitable for further thermalcracking tr atment, are condensed.in this zone as reflux condensate. Inthe particularcase here illustrated, the total reflux condensate isdirected from fractionator I0 through line 83 and valve 84 to pump 85and supplied therefrom through line 86 and valve 81 to fractionator l3,wherein it commingles with 'the other materials supplied to this zone aspreviously described and is separated therewith into the desiredfractions, as previously explained. Thus, the motor gasoline recoveredin receiver 42 will normally contain heavy gasoline fractions I producedin the low temperature catalytic cracking step and the cracking stocksupplied to coil 6 and/or to coil ill will include conversion productsproduced in the low temperature catalytic cracking step which boil abovethe range of the motor gasoline.

It is, of course, also within the scope of the invention to separatelyremove the high endpoint gasoline fractions as a side stream fromiractionator l0 and recover the same a a sepnot illustrated, to the up-.

a'rate product of the process or blend them, in regulated. quantities,with the motor gasoline resulting from thermal cracking treatment,although well known means for accomplishing, this are, for the sake ofsimplicity, omitted from the drawing; In such cases the heavierfractions of the catalytic conversion products suitable for furtherthermal cracking treatment may be supplied fronr fractionator tofractionator l3" or directly from fractionator T0 to cracking coil 6 orto cracking coil I 0, as desired.

It is not intended to limit the invention to the use of any specifictype of low temperature catalytic cracking catalyst since there areseveral which aresuitable under properly controlled con- .ditions oftemperature, pressure and contact time and, apart from the method ofoperation herein provided, such suitable catalysts are not a novel partof the present invention. Certain naturally,

occurring or synthetically prepared catalysts comprising alumina andsilica, alone or together with other materials, such as oxides ofzirconium,

- thorium or the like or combinations of silica with zirconia and/orthoria or other metal oxides, may be successfully employed. I alsocontemplate the use of aluminum chloride and other well known crackingcatalysts. terial which I have found particularly suitable is silica,prepared from silica gel or the like, comprising a carrier for regulatedamounts of aluminaor zirconia, or both, and preferably subistantiallyfree of alkali metals which fuse at tem,- peratures such as thoseencountered during re- However, the catalytic maactivation and therebytend to reduce or destroy.

the activity of the catalyst.

Preferably,v as previously mentioned, a temperature of the order of 650to 800 F., or thereabouts, is employed in the low temperature catalyticcracking step with relatively low superatmosphericpressures of the orderof to 150 pounds,or thereabouts, per square inch and pref,- erably witha space velocity, expressed as the volume of hydrocarbons subjected tocatalytic treatment in a given time per unit volume of catalyticmaterial of the order of 0.75 to 2. .However, at the present time, thelimits of temperature, pressure and contact time, within which pounds,or thereabouts, per square inch. The reaction chamber is preferablyoperated at a superatmospheric pressure of the order of 100 to 500pounds per square inch and a substantially reduced pressure of the orderof 30 to 150 pounds per square inch is preferably employed in thevaporizing and separating chamber, with the succeeding fractionating,condensing and vcollecting equipment operated at substantially the sameor somewhat lower pressure. As an example of one specific operation ofthe process'as conducted in a system such as illustrated .in thedrawing, the charging stock is a Mid-Continent topped crude ofapproximately 25 A. P. I. gravity which is supplied to the fractionatorof the system and therein separated, together with the components of thethermal and low temperature catalytic conversion products supplied tothis zone which boil above the range of the motor gasoline, intorelatively light and relatively heavy reflux condensate fractions. Theheavy reflux condensate is heated in the heavy oil cracking coil to anoutlet temperature of approximately 910 F. at a superatmosphericpressure of about 225 pounds per square inch and the resultingconversion products are supplied to' the reaction chamber which isoperated at substantially the same pressure. The light reflux condensateis heated in the light oil cracking coil to an outlet temperature ofapproximately 975 F. at a superatmospheric pressure at this point in thesystem of approximately 350 pounds per square inch and the conversionproducts from the light oil cracking coil are also supplied to thereaction chamber. Both vaporous and liquid conversion products areremoved from the lower portion of the reaction chamber'at a temperatureof approximately 900 F., cooled to approxilow temperature" catalyticcracking may be successfully accomplished with various types of chargingstocks and various catalysts, have not been completely explored and theindications are that temperatures outside the range above given andparticularly from 500 to 850 F.' or slightly higher and space velocitiesof from 0.25 to 4 are suitable for some charging stocks andsome types ofcatalyst. I believe, however, that the more limited range of operatingconditions above given will generally hold for the treatment of crackedvapors, derived as herein described, with the preferred type of catalystabove mentioned.

The conditions of operation employed in the thermal cracking phase ofthe system will vary within relatively wide limits, depending upon thetype of charging stock employed and the specific form of crackingequipment utilized. In a system such asillustrated and above described,the temperature employed at the outlet of theheavy oil cracking coil mayrange from 800 to 925 F., preferably with a superatmospheric pressure atthis point in the system of from 100 to 500 pounds, or thereabouts, persquare inch. The temperature employed at the outlet of the light oilcracking coil is preferably ofthe order of 900 to 1025 F., with asuperatmospheric pressure at 400 F. is recovered.

mately 830 F. and supplied to the vaporizing and separating chamber at asuperatmospheric pressure of approximately pounds per square inch. Thetemperature of the vapors leaving the vaporizing and separating chamberis approximately 770 F. and about 50% of this vaporous stream suppliedto the low temperature catalytic cracking step. The vapors enter thecatalytic reactor at a temperature of approximately 750 F. Asubstantially uniform temperature of approximately 750 F. is maintainedin the catalytic reaction zone and the resulting conversion products aresupplied therefrom to the fractionator of this stageof the system at asuperatmospheric pressure of approximately 35 pounds per square inch. Anaviation-base gasoline of approximately 300 F. end-boiling point isrecovered from the catalytic conversion products and the remainder ofthe latter, except for a small amount of-the residual liquid fractionsseparated therefrom, is supplied to the fractionator of the thermalcracking step wherefrom motor gasoline having an end-boiling point ofapproximately The above described operation will yield, per barrel ofcharging stock, approximately 32% of motor gasoline, which includesheavy gasoline .fractions produced in the low temperature catalyticcracking step, andapproximately 22% of the 300 F. end-pointaviation-base gasoline. The residual liquid produced amounts'toapproximately 38% of the charging stock and the remainder of the latteris chargeable principally to normally gaseous products. The 400 F. endpoint gasoline has a relatively high content of oleflns' and aromaticsand an octane number of approximately 68. The 300 F. end point gasonoincreased temperature or pressure containing fractions boiling line hasan octane number of about '70, which quantity of aromatics to raise itscold test to ,above market requirements.

l2 claim as my invention: -1. The process of hydrocarbon oil conversionwhich comprises thermally cracking an oil under conditions regulatedto'produce therefrom high yields of gasoline sufliciently high in olefincontent to render it-unsuitable as aviation gasoline, separating theresulting products into vapors suit able for catalytic cracking andnon-vaporous residue under conditions which leave said vapors atsufficient temperature and pressure to initiate catalytic crackingthereof in the presence of a cracking catalyst, separating said vaporsinto two streams of substantially thesame composition, initiallycontacting one of said streams at with said cracking catalyst in a zonewherein contact is continued for a time and under temperature andpressure conditions regulated to increase the gasoline content reduceits olefin content, recovering from the roducts of the catalyticcracking step a gasoline fraction meeting market specifications foraviation gasoline with respect to boiling range and acid heat test,further separating from.the products of the catalytic ,cracking step acondensate consisting essentially of fractions boiling above the rangeof said aviation gasoline,

commingling said condensate with said other stream of vapors andfractionating the mixture to form reflux condensate and a vaporousstream comprising motor gasoline of higher end boiling point and higherolefin content than said aviation gasoline, condensing and recoveringsaid motor gasoline and supplying reflux condensate formed by saidfractionation to the thermal cracking step.

2. The process of hydrocarbon oil conversion which comprises thermallycracking an oil under conditions of elevated temperature and substantialsuperatmospheric pressure, separating the resulting products into vaporsand non-vaporous residue at substantially reduced super-atmosphericpressure and at a temperature of the order of 600-850 F., contacting aregulated quantity of said vapors at substantially the same temperatureand no higher pressurewith a catalyst which promotes theirlowtemperature catalytic cracking, separating from the resultingproducts of the catalytic cracking step a fractionated vaporous streamcomprising aviationbase gasoline and a higher boiling condensate abovethe range of said aviation-base gasoline, supplying another portion ofthe first named vapors and said higher boiling condensate to a separatefraction ating step and therein fractionating the mixture 'to formreflux condensate and a fractionated vaporous stream comprising motorgasoline of higher end boiling point and higher olefin content than saidaviation-base gasoline, supplying reflux condensate formed in the lastnamed fractionating step to the thermal cracking operation andseparately recovering from said fractionated vaporous streams saidaviation-base gasoline and said motor gasoline.

,3. The process of hydrocarbon oil conversion which comprises thermallycracking an oil under conditions regulated to produce therefrom highyields of gasoline of relatively high olefin content, separating theresulting products .into vapors suitable for catalytic cracking andnonvaporous residue, separating said vapors into at least two streams ofsubstantially the same composition, subjecting one of said streams tocatalytic cracking under conditions of temperature, pressure and contacttime regulated to increase the total gasoline content of the vapors andmaof said stream and materially terially reduce its olefin content,fractionating the resulting catalytically cracked products to formreflux condensate and to recover therefrom gasoline fractions meetingmarket specifications for aviation-base gasoline, combining the refluxcondensate with another of -said streams and separating an automotivegasoline from the mixture, of higher olefin content than said aviationgasoline.

4. The process of hydrocarbon oil conversion which comprises thermallycracking an oil under conditions regulated to produce therefrom highyields of gasoline of relatively high olefin content, separating theresulting products into vapors suitable for catalytic cracking andnonvaporous residue under temperature and pressure conditions at whichfurther cracking of the resulting vapor can be initiated in the presenceof a cracking catalyst, separating said vapors into at least two streamsof substantially the same composition, subjecting one of said streams tocontact with said cracking catalyst under conditions of temperature andpressure approximating those obtaining in the first mentioned separationstep and for a contact time regulated to increase the pors andmaterially reduce its olefin content, fractionating the resultingcatalytically cracked products to form refluxcondensate and to recovertherefrom gasoline fractions meeting market specifications foraviation-base gasoline, combining the reflux condensate with another ofsaid streams and separating an automotive gasoline from the mixture, ofhigher olefin content than said aviation-base gasoline.

( CHARLES W. HUSSEY.

total gasoline content of the Va-

